Tom Mathew

Indian Institute of Technology Bombay | IIT Bombay ·  Department of Civil Engineering

The land passenger transport sector lies on the cusp of a major transformation, guided by last mile connectivity, digital technology, and collaborative consumption. The recent emergence of transportation network companies, in tier-I cities of developing countries, which provide economically and environmentally convenient sharing services over the l...

Surrogate measures of safety (SMoS) aims at road safety evaluation without depending on historical crash data. Existing studies have evaluated SMoS in traffic conditions having good lane discipline. However, in several traffic conditions vehicles do not follow good lane discipline resulting in high crash rates. Moreover, existing studies do not con...

Signalized intersections are major locations of congestion and delay in a corridor. Accurate estimation of capacity at the signalized intersection is important to ensure optimal signal timings that minimize delay. Mixed traffic is characterized by the presence of diverse vehicle types, each having its own static and dynamic characteristics. This gi...

Vehicular emission models are important tools in several environmental impact studies. Although several studies have been conducted for emission control purposes, few attempts have been made on the planning side. For instance, long-term transportation network capacity improvement models do not explicitly consider emission in the objective function....

State and local transit agencies require government support to preserve their aging transit fleets. With the passage of time, transit fleets get older and require maintenance costs to keep them operational. To provide services at a desired level, transit agencies must maintain a minimum fleet size. Two imperative considerations from the transit pla...

The traffic flow at intersections is generally chaotic, and signalization is a control measure to reduce this chaos. Heterogeneous traffic at signalized intersections behave much differently from homogeneous traffic. Also, in many countries, nonlane-based traffic prevails; hence, designing control systems for such situations is a challenging task....

Car-following behaviour is well studied and analyzed in the last fifty years for homogeneous traffic. However in the mixed traffic, following behaviour is found to vary based on type of lead and following vehicles. In this study, a neural network based model is proposed to predict the following behaviour for different lead and following vehicle-typ...

Conventional transportation network design problems treat origin-destination (OD) demand as fixed, which may not be true in reality. Some recent studies model fluctuations in OD demand by considering the first and the second moment of the system travel time, resulting in stochastic and robust network design models, respectively. Both of these model...

Existing optimal road-network capacity-expansion models are based on minimizing travel time and rarely consider environmental factors such as vehicular emissions. In this study we attempt to solve such a transportation network design problem when the planner is environment conscious and thereby tries to minimize health-damage cost due to vehicular...

Car-following models replicate the behavior of a driver following another vehicle and are widely used in the development of traffic simulation tools. In this study, the performance of major car-following models is evaluated using microscopic vehicle trajectory when the lead and the following vehicle-types are different. Vehicles equipped with Globa...

Signalisation is a traffic control strategy to ease the competition by providing right-of-way in a cyclic manner to conflicting traffic at intersections. Saturation flow is a major component in the design of signals, and is influenced by a variety of factors like vehicle composition, intersection geometry and driver's behaviour. The highway capacit...

Accessibility constraints due to traffic congestion resulting from vehicular growth is a major transportation related problem in urban areas. Increasing road infrastructure to reduce traffic congestion is a highly expensive prop osition. Controlling traffic signal timing in an optimal condition is undoubtedly one of the most cost -effective means o...

Most transit agencies require government support for the replacement of their aging fleet. A procedure for equitable resource allocation among competing transit agencies for the purpose of transit fleet management is presented in this study. The proposed procedure is a 3-dimensional model that includes the choice of a fleet improvement program, age...

The writers present a procedure for resource allocation among transit agencies for transit fleet management, specifically focusing on the purchase of new buses and rebuilding of existing buses. The model is formulated as a nonlinear optimization problem of maximizing the total weighted average remaining life of the fleet subject to budgetary, polic...

A significant part of the world, especially in most of the Asian countries, has heterogeneous traffic characterized by diverse vehicles, changing composition, lack of lane discipline, etc., resulting in a very complex behavior. Microsimulation is, therefore, highly suited to model such traffic. However, these models need to be calibrated before the...

A study was done to formulate and solve the multiobjective network design problem with uncertain demand. Various samples of demand are realized for optimal improvements in the network while the objectives of the expected total system travel time and the higher moment for total system travel time are minimized. A formulation is proposed for multiobj...

A traffic network design problem attempts to find optimal network expansion policies under budget constraints. This can be formulated as a bilevel optimization problem: the upper level determines the optimal link capacity expansion vector and the lower level determines the link flows subject to user equilibrium conditions. The upper level is a capa...

The critical component of all emission models is a driving cycle representing the traffic behaviour. Although Indian driving cycles were developed to test the compliance of Indian vehicles to the relevant emission standards, they neglects higher speed and acceleration and assume all vehicle activities to be similar irrespective of heterogeneity in...

A grid based modelling approach akin to cellular automata (CA) is adopted for heterogeneous traffic flow simulation. The road space is divided into a grid of equally sized cells. Moreover, each vehicle type occupies one or more cell as per its size unlike CA traffic flow model where each vehicle is represented by a single cell. Model needs inputs s...

This article addresses the problem of a traffic network design problem (NDP) under demand uncertainty. The origin–destination trip matrices are taken as random variables with known probability distributions. Instead of finding optimal network design solutions for a given future scenario, we are concerned with solutions that are in some sense “good”...

This study presents an attempt to simulate heterogeneous traffic using the principles of cellular automata. A conventional cellular automata model for the homogeneous traffic is modified to handle heterogeneity. The principle adopted in this study is to retain the passenger car equivalent concept of HCM and the basic structure of the CA model. The...

Traffic network design problem attempts to find the optimal network expansion policies under budget constraints. This can be formulated as a bi-level optimization problem: the upper level determines the optimal link capacity expansion vector and the lower level determines the link flows subject to user equilibrium conditions. However, in the contex...

Recent interest in developing activity-based models of transport demand has encouraged research on the design and administration of activity diaries. Activities occur in time and space. Traditionally, these two dimensions have been bifurcated. Time-use diary researchers focused oil activities whereas travel diary researchers centered on trips. Howe...

A methodology for determining optimum cell size for a grid based traffic flow model for heterogeneous traffic is proposed in this paper. The cell size is an important factor to determine as it affects the computational efficiency and model accuracy. The objective function minimizes three aspects namely the difference of distance headway in case of...

There have been few attempts to describe traffic behaviour in highly-congested urban road environments characterised by a wide range of vehicular types. Such environments can be found in many Asian cities where user behaviour is perceived as more 'chaotic' than that occurring in countries such as Australia and New Zealand where adherence to rules,...

A transit route network design (TRND) problem for urban bus operation involves the determination of a set of transit routes and the associated frequencies that achieve the desired objective. This can be formulated as an optimization problem of minimizing the total system cost, which is the sum of the operating cost and the generalized travel cost....

Traffic congestion is the most visible manifestation of the failures in urban traffic operations. It is a widely recognised that relief from providing more roadway space in urban areas has been only temporary and the concept of traffic management has not been successfully adopted. A considerable amount of traffic congestion in cities is caused not...

In this paper, the authors present a single-stage optimization model that can be used to allocate limited resources among transit agencies for the purchase of new buses and for rehabilitation of the existing buses. The model is formulated as a non-linear optimization problem of minimizing the total weighted average remaining life of the fleet subje...